Commitments and Contingencies (Details) (USD $)	3 Months Ended		6 Months Ended			1 Months Ended													6 Months Ended				1 Months Ended				1 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Apr. 30, 2012 Restricted for Litigation Costs [Member]	Dec. 31, 2011 Restricted for Litigation Costs [Member]	Jun. 30, 2012 Equipment Leases [Member]		Jun. 30, 2012 Service Payments [Member]	Jun. 30, 2012 Facility Leases [Member]		Jun. 30, 2012 Buildings, Avenue of Americas [Member]	Dec. 31, 2011 Buildings, Avenue of Americas [Member]	Jun. 30, 2012 Clawback Obligation [Member]		Jun. 30, 2012 Unfunded Commitments [Member] investments		Jun. 30, 2012 Commitment to Invest [Member] Cowen Healthcare Royalty Partners [Member] Affiliated Entity [Member]		Jun. 30, 2012 Commitment to Invest [Member] Cowen Healthcare Royalty Partners [Member] Affiliated Entity [Member] Minimum [Member]	Jun. 30, 2012 Commitment to Invest [Member] Cowen Healthcare Royalty Partners [Member] Affiliated Entity [Member] Maximum [Member]	Apr. 30, 2011 Commitment to Invest [Member] Starboard Value L.P. [Member] Affiliated Entity [Member]		Jun. 30, 2012 Unfunded Commitment to Invest [Member] Starboard Value L.P. [Member] Affiliated Entity [Member]		Apr. 30, 2012 Indemnification Agreement [Member] Restricted for Litigation Costs [Member]	Dec. 31, 2011 Indemnification Agreement [Member] Restricted for Litigation Costs [Member]
Lease Obligations
Net rent expense	$ 3,700,000	$ 3,300,000	$ 7,400,000	$ 6,900,000
Liability relating to vacating premises													4,400,000	5,700,000
Future minimum annual lease and service payments
2012								1,650,000	[1]	5,580,000	8,777,000	[2]
2013								3,301,000	[1]	9,411,000	17,632,000	[2]
2014								1,548,000	[1]	7,428,000	15,376,000	[2]
2015								1,051,000	[1]	2,065,000	12,293,000	[2]
2016								194,000	[1]	194,000	11,404,000	[2]
Thereafter								0	[1]	0	53,585,000	[2]
Future minimum annual lease and service payments								7,744,000	[1]	24,678,000	119,067,000	[2]
Sublease income related to operating leases	300,000	100,000	800,000	200,000
Contractual obligation															6,200,000	[1]	6,000,000	[1]	42,200,000	[1]					2,900,000	[1]
Number of real estate investments, in investments																	2
Funding toward commitments																			25,900,000	[1]
Commitments made																							15,000,000	[1]
Expected call period																					2 years	5 years
Restricted cash	9,257,000		9,257,000		9,785,000		500,000																					500,000
Cash released from escrow						$ 500,000																					$ 500,000

[1] Equipment Leases include the Company's commitments relating to operating and capital leases. See Note 14 for further information on capital lease minimum payments.

[2] The Company has entered into various agreements to sublease certain of its premises. The Company recorded sublease income related to these leases of $0.3 million and $0.1 million for the three months ended June 30, 2012 and 2011, respectively, and $0.8 million and $0.2 million for the six months ended June 30, 2012 and 2011